Cosmologic philosophy: multiverse/inflation theory (Introduction)

by David Turell , Wednesday, December 30, 2015, 15:41 (3251 days ago) @ David Turell

A very long review article on the current state of cosmologic research:-https://aeon.co/essays/will-we-ever-understand-the-beginning-of-the-universe?utm_source=Aeon+Newsletter&utm_campaign=8a114bbdda-Daily_newsletter_Wednesday_30th_Dec12_22_2015&utm_medium=email&utm_term=0_411a82e59d-8a114bbdda-68942561-"'But cosmology's hot streak has stalled. Cosmologists have looked deep into time, almost all the way back to the Big Bang itself, but they don't know what came before it. They don't know whether the Big Bang was the beginning, or merely one of many beginnings. Something entirely unimaginable might have preceded it. Cosmologists don't know if the world we see around us is spatially infinite, or if there are other kinds of worlds beyond our horizon, or in other dimensions. And then the big mystery, the one that keeps the priests and the physicists up at night: no cosmologist has a clue why there is something rather than nothing.-"To solve these mysteries, cosmologists must make guesses about events that are absurdly remote from us. Guth's theory of inflation is one such guess. It tells us that our Universe expanded, exponentially, a trillionth of a trillionth of a trillionth of a second after the Big Bang. In most models of this process, inflation's expansive kick is eternal. It might cease in particular parts of the cosmos, as it did in our region, after only a fraction of a second, when inflation's energy transformed into ordinary matter and radiation, which time would sculpt into galaxies. But somewhere outside our region, inflation continued, generating an infinite number of new regions, including those that are roaring into existence at this very moment.-***-"When you read that word cosmos, you might begin to imagine the most expansive physical world your mind can build. Deep fields of glittering, star-filled galaxies stretching out in every direction, and maybe into forever. But even that image represents only the barest sliver of what is meant by ‘cosmos'. To build a cosmos, you have to extend your imagination to all of space and all of time. Only one of Earth's creatures can pull off that cognitive trick. All living things are attuned to their environment: bacteria can sense chemical shifts in their immediate surroundings; migrating birds know our planet well enough to wing annually across its whole face; dung beetles navigate by the light of the Milky Way. But only the human being lives inside a cosmos, and only recently.-***-"Inflation could turn out to be right in the end. Some of its predictions have come true. At the moment, there is no alternative theory of the early Universe that explains more. But cosmologists should be searching for one. They should not be waving away inflation's fine-tuning problems with the multiverse. Until eternal inflation is testable and tested, successfully, again and again, cosmologists should not allow it to monopolise the collective theoretical imagination. Inflation is a speculative theory, and it should be treated as such.-***-"The real trouble with eternal inflation's multiverse is that it can't be tested, at least not yet. We can't put a telescope in the regions outside ours. We have to look for evidence of the multiverse in our region. What should we look for? It's hard to say, because the multiverse explores every combination of cosmic conditions an endless number of times. It's not clear that any combination is likelier than any other. Theorists are trying to determine whether some conditions are more probable than others, but they haven't succeeded yet, and there's no guarantee they will. In the meantime, it's hard to know whether inflation's fine-tuning problems are genuine explanatory gaps that need exploring, or quirky outcomes of the quantum slot machine. The theory's weaknesses can be explained away with the same glib shrug that accompanies the retort: ‘God just made it that way.'"-Comment: Well worth the long read